There is currently a market-driven need to extend the phase count in multi-phase DC-DC regulator systems beyond a number that can be practically supported by conventional multi-phase systems. Multi-phase systems use a controller to regulate the power delivered by more than one power channel to a load. In many conventional systems, the controller regulates the voltage level at the load by sending each remote power channel a stream of PWM with precisely controlled widths. These PWM signals are sequenced and timed such that the interval between rising edges (or in some implementations, falling edges) of pulses delivered to each remote power channel is constant.
In typical implementations, each power channel includes a channel driver integrated circuit (IC) and a power stage containing one or more power semiconductor switches. In a conventional system, a supervisory controller IC regulates the pulse width of each of the connected driver ICs. Each of the connected driver ICs, in turn, controls a semiconductor switch to periodically connect the input power source to the output load. In many instances, the driver IC also controls a second semiconductor switch in a method commonly known as synchronous rectification. These systems often measure the current from each power channel and use the information to modify the pulse widths independently in a manner that effectively equalizes the current delivered by each power channel. The sum of the current measurements is also used to precisely regulate the output resistance in a method commonly known as droop regulation or load-line regulation. Both of these functions are commonly implemented in the controller, so that signals must be transmitted from the remote power channels back to the controller.
In a conventional multichannel layout, such as that outlined above, there are at least two signals between the controller and each power channel. In some implementations, there are three signals between each power channel and the controller, while in other, less-common implementations, there may be eight or more. Since the number of pins on the controller dedicated to communicating with the power channels increases along with the number of power channels, there is a corresponding increase in the cost of the controller and in the difficulty of routing the signal traces near the controller.
Moreover, the distances from the controller to the most remote power channels increase as the number of power channels increases. This compounds the difficulty faced by the system designer to preserve signal integrity of the sensitive current-sense lines as they traverse long distances through a noisy environment. This is due to the fact that the signals transmitted on the current-sense lines are voltage signals proportional to current, and voltage signals are prone to corruption from capacitively-coupled noise.